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The power hybridization characteristics of LPG-HEV city buses in real world and the relation between degree of hybridization (DOH) and vehicle operating conditions are studied in this paper. A series of on-board tests were performed on LPG-HEV buses operated in Guangzhou City, China. Portable Emission Measurement System (PEMS) and CAN-BUS were used to sample vehicle and power battery parameters and information, such as instantaneous speed and torques of engine and motor, vehicle speed and working states of power batteries, etc. Vehicle acceleration, driving power and DOH were calculated based on the experimental data. The relationships between vehicle operating conditions, working states of power batteries and DOH were analyzed. The study results show that the LPG-HEV city buses are mainly operated at the DOH range from 15% to 40%, it means that the hybridization is moderate. In starting stage, DOH reached the maximum which is higher than 80% when the speed is less than 2km/h.

This paper studies the characteristics of fuel consumption and exhaust emission of city transit buses, and analyzes the fuel saving rate and exhaust pollutants reduction effect of LPG-HEV buses relative to LPG buses. The running speed, fuel consumption, exhaust emission and other variables of 3 LPG-HEV buses that aren't plug-in hybrid, and 2 LPG buses were measured by a portable emission measurement system (PEMS) under real driving situations of city transit buses in Guangzhou, China. The test data was analyzed to make a comparison between LPG-HEV and LPG buses. The study results show that the running speed of city buses in real driving modes is mainly distributed in the range of 0 to 35 km/h, and the average value is 18km/h, while the acceleration is distributed in a range from −0.5 to 0.5m/s2 mainly. The average fuel consumption of LPG-HEV buses is 51.02 l/100km, and is 6.23% lower than that of LPG buses.